Known dishwashers comprise a washing tub in which usually one or two horizontal shelves are provided to hold the dishes to be washed, where within the tub a plurality of spray nozzles or spray rotors are provided to direct a washing liquid towards the dishes. The washing liquid can be water or a mixture of water and a detergent (for simplification in the following also referred to as “water”) and is collected in a sump which is located at the bottom of the tub in which is fluidly connected to a drain pump and a circulation pump. The drain pump is provided for sucking in water out of the sump and pumping it out of the dishwasher (e.g. at the beginning and/or at the end of a wash cycle), whereas the circulation pump is provided for pumping the water up to the nozzles in order to sustain the circular flow of water from the sump up to the nozzles and again back to the sump.
The circulation pump may work at different speeds according to the desired pressure at the nozzles. Usually, when the sump is completely filled with water, the circulation pump is started and sucks in water in order to provide for the circular flow.
At the beginning of a washing cycle known dishwashers start a drain step where the drain pump is started in order to be sure that there is no water remaining in the sump (from a previous washing cycle). This operation is also performed in a situation where the sump is already empty and consumes electrical power and produces noise. At a later phase known dishwashers load a fixed amount of water depending on the signal from a pressure switch or sensor detecting the current water level.
It is an object of the present invention to provide for improved methods and an improved dishwasher where the power consumption as well as the noise emission is reduced.